1. Field of Invention
The present invention relates to an electronic circuit for driving a current-driven element such as an organic light emitting diode element, a method of driving the same, an electro-optical device, and an electronic apparatus.
2. Description of Related Art
Attention is paid to an organic light emitting diode (hereinafter, referred to as OLED) element as a next generation light emitting device that replaces a liquid crystal element. The OLED element is referred to as an organic electroluminescent element or a field emission polymer. Since the OLED element is a spontaneous emission type, it has less dependency on a viewing angle. Also, since the OLED element does not need back light or reflected light, it consumes less power and is made thinner. As a result, the OLED element has good characteristics as a display panel.
Here, the OLED element is a current type element to be driven that does not have a voltage storage property unlike a liquid crystal element and that cannot maintain a light emitting state when current is interrupted. Thus, when the OLED element is driven by an active matrix method, a voltage storage element such as a capacitor is inserted between the gate of a driving transistor that supplies current to the OLED element and an electrostatic potential line and a voltage corresponding to the grayscales of pixels is written in the gate of the driving transistor during a selection period. According to such structure, since the gate voltage is stored in a non-selection period due to the capacitor of the driving transistor, it is possible to continuously flow current corresponding to the corresponding gate voltage to the corresponding OLED element.
According to such structure, since the threshold voltage characteristic of the driving transistor is not uniform, the brightness of the OLED element varies in each pixel circuit, which deteriorates the quality of displayed images. Thus, recently, a technology of connecting the driving transistor to a diode to perform programming such that current flows from the driving transistor to data lines and such that a target voltage corresponding to the current to flow through the OLED element is written in the gate of the driving transistor to compensate for non-uniformity of the threshold voltage characteristic of the driving transistor (for example, refer to Patent documents 1 and 2)
[Patent Document 1] U.S. Pat. No. 6,229,506 (refer to FIG. 2)
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2003-177709 (refer to FIG. 3)